Objective quantification of bleb function using swept source anterior-segment optical coherence tomography

Abstract

Purpose : Evaluation of bleb function typically relies on subjective assessment of en-face morphological features on slit-lamp examination. This study evaluates the use of anterior-segment OCT (AS-OCT) and image texture analysis to provide objective, quantifiable parameters of bleb function in eyes that have undergo trabeculectomy and non-penetrating Deep Sclerectomy surgery.

Methods : Cross-sectional study of 204 blebs of 120 patients who had undergone trabeculectomy (Trab, n=96) or deep sclerectomy (DS, n=108) surgery at least one year prior for glaucoma. AS-OCT was used to capture filtering blebs in the sagittal plane. Standardized regions of interest (measuring 400x800 pixels) bisecting the sclerostomy/trabeculo-descemet window and scleral flap and just proximal to the peripheral cornea were cropped and segmented.

Results : The median post-operative follow up was 8.4 (IQR 3.2-9.0 years). Complete success (CS; IOP ≤18mmHg with no medications), qualified success (QS; IOP ≤18 with medications) and failure (F; IOP>18mmHg) in the Trab and DS cohorts were 37.3%, 32.7% and 30.0% respectively. In Trab blebs, mean pixel intensity (PI) was significantly lower in CS as compared to QS and F blebs (150.8 +/- 14.5 vs 157.4 +/- 13.4 vs 167.4 +/- 13.5, p = 0.0001). Standard deviation of pixel intensity values and solidity were also significantly lower in CS and QS as compared to F in both Trab (Figure 2). Sagittal area values of blebs were significantly greater in CS and QS groups compared to F in both Trab and DS cohorts. A moderate inverse correlation was observed between maximal bleb height and PI in both Trab (r= -0.49, p<0.0001) and DS (r=-0.46, p<0.0001) groups.

Conclusions : Image intensity and bleb area values of AS-OCT sagittal slices were significantly associated with CS compared to QS and F. These quantitative parameters may be used to objectively evaluate bleb function in clinical practice. may help guide pharmacological treatment/early surgical intervention in the post-operative period in glaucoma surgery.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.

 

Figure 1: AS-OCT image of a trabeculectomy bleb (A), with region of interest (ROI) (B). Representative blebs in CS (C), QS (D) and F (F).

 

Figure 2: Pixel intensity, standard deviation (pixel variance), and sagittal area values across the outcome groups of CS, QS and F in Trab (A, B, C) and DS (D, E, F) cohorts. p < 0.05 (*), < 0.01 (**), < 0.001 (***), < 0.0001 (****)